1. Field of the Invention
The present invention relates to a self-weight pressure control valve located on a liquid supply path usable to supply a liquid from a liquid supply to a liquid injector, a liquid supply system including the same, and an inkjet recording device.
2. Description of the Related Art
An inkjet recording device for industrial use or the like adopts a structure in which a large capacity ink cartridge is located away from a carriage having an ink injection head mounted thereon, namely, an off-carriage system. Generally, in a recording device of the off-carriage system, an ink supply path usable to supply ink from the ink cartridge to the ink injection head is long. As a result, the ink pressure fluctuation is large in the ink supply path, and thus there may be a case where the ink is not injected stably from the ink injection head.
In such a situation, it has been conventionally desired to suppress the ink pressure fluctuation low. For example, WO2003/041964 discloses a structure in which an ink injection head and a valve unit are mounted on a carriage. The valve unit is a self-sealing valve, and has a function of adjusting the pressure of ink to be supplied to the ink injection head (self-sealing function). With the above-described structure, the ink is transmitted to the ink injection head at a predetermined pressure, and thus the ink is injected stably from the ink injection head.
The valve unit described in WO2003/041964 is put into a self-sealing state by a function of an urging member that urges the valve in such a direction as to close the valve. The urging member is, for example, a coiled seal spring. The seal spring is located at such a position as to be in contact with the ink. However, the seal spring is very small and coiled, and therefore, does not have a sufficient area size or thickness to be, for example, plated in order to improve the ink corrosion resistance. For this reason, the seal spring may be corroded and deteriorated after being used for a long time in the case where, for example, the ink contains a certain component. When the seal spring is corroded and deteriorated, the elastic force of the spring is decreased, and thus the urging force acting in such a direction as to close the valve is weakened. As a result, the self-sealing state is not stably maintained, which may cause a state where, for example, the injection of the ink during printing (during ink injection) is made unstable. In addition, while the printing is not performed, the ink may leak from the ink injection head.